1. Field of the Invention
The present invention is directed to creping machines installed between a mat reception and shaping hood and a polymerizing oven.
2. Description of the Related Art
Creping machines are installations of which the aim is to rearrange the fibers in a mat of mineral wool fibers sized with a non-polymerized binder. The creping machine is installed between the mat reception and shaping hood and the binder polymerizing oven. In principle it comprises at least one pair of continuous conveyors with superimposed belts. It is intended to alter the orientation and arrangement of the mineral wool mat fibers which pass over it, generally by means of compression, not only of the thickness but also of the length of the product. Longitudinal compression is produced by reducing the velocity by which the mat passes between the successive reception, creping and oven conveyors.
The creping machine may comprise one or more pairs of conveyors. For example if there are three pairs, the first pair can be synchronous with the mineral wool mat reception velocity and the third pair synchronous with the advance of the mat in the oven, while the second pair can be regulated at an intermediate velocity, depending on the product manufactured.
FIG. 1 illustrates the principle of a known type of creping machine. The gap between a first pair of continuous conveyors 1 and 2 decreases as a mineral wood mat (not shown) passes between them in the direction of the arrow 3. A second pair of continuous conveyors 4 and 5 converge in an extension of conveyors 1 and 2. These two pairs of conveyors 1-5 compress the mineral wool mat in the direction of its thickness. The drive velocity of the second pair of conveyors 4, 5 is slower than that of the first pair 1, 2, which results in longitudinal compression of the mat.
A third pair of conveyors 6, 7 follows the second pair 4, 5 and moves at a slower velocity than that of this second pair. The distance between the active runs of the conveyors 6, 7 is constant. This third pair 6, 7 thus increases only the longitudinal compression of the mat.
Taking this principle as a starting point, conveyor belts were initially used in a creping machine producing a 1.2 m wide mat. The belts were of the type known by the name of "TISSMETAL". These belts are made entirely of metal and designed with two roller drive chains, one on each edge. These two chains are connected transversely to metal bars by means of special attachments. The belt itself consists of metal woven about transverse bars. These belts are driven by pinions acting on the two chains of which one is located on each edge. In order to absorb and support the compression stresses resulting from the progressive crushing of the mineral wool mat between the belts, the woven metal rubs against the steel sliding tables.
The major drawbacks of these metal conveyors are: a) restriction of the continuous running velocity to 40 m/min with peaks which may reach 50 m/min depending on the supplier; experience has shown that the operation of these conveyors at velocities of this type causes an enormous amount of vibration and results in the frequent breaking of the transverse bar mountings; b) large-scale fouling of the woven metal by the sized fibers, hence awkward cleaning of the machine with pressurized water whenever it has been used; c) considerable maintenance work of the chain mechanism drive system of these conveyors owing to oxidation, fouling and vibrations.
In order to avoid these disadvantages and in particular to operate and produce at higher speeds, the metal belts have been replaced by conveyor belts made from synthetic materials, for example "SIEGLING" belts, the width of the mineral wool mat still being 1.2 m.
The average diameter of the creping machine conveyor rollers must be as small as possible and in any case restricted to 125 mm in order to avoid damaging the creped product. In effect, the mat must pass from one conveyor to another over a distance which is very small so as not to interrupt the creping effect in the product. It is evident that increasing the diameter of adjacent rollers means a larger void when the product passes from one conveyor to another.
This constraint imposed by the roller diameter restricts the surface area available for driving the conveyor belts. In view of the existing constraints on belts (pressure of the mineral wool creped product assessed as being 500 daN/m.sup.2), the diameter of the smooth steel drive roller should be at least 160 mm. Since this value is incompatible with what has been stated above, it was necessary to provide an arrangement as shown in FIG. 2, where only the end of the second pair of conveyors and the third pair are illustrated in order to show the conveyor belt drive means which are the same for all three pairs of conveyors.
The belt 8 is driven by a steel drive drum 9 which is 153 mm in diameter and covered with rubber with a shore hardness of approximately 80.degree. to 90.degree., in order for there to be a high friction coefficient between the drum 9 and the belt 8.
In order to ensure that the belt 8 is driven correctly, two tension rollers 10, 11 have to be provided in this case. At 12 there is illustrated schematically the creped mineral wool mat ready to pass, along direction 13, into the polymerization oven which is not shown. Two roller 14 and 15 return the belt 8 and have a maximum diameter of 125 mm for the reason indicated above.
A belt 8', disposed symmetrically to 8, completes the third pair of conveyors. It is driven by a drive roller 9', identical to 9, and passes over two tension rollers 10', 11', identical to 10 and 11, and about two return rollers 14', 15', identical to 14 and 15.
In order to improve the guiding of the belt 8 or 8' respectively, the drive drum 9, or 9' respectively, is machined so as to be cylindrically conical (FIG. 3) and the belts 8, 8' have trapezoidal projections 16 running along their edges. The belt 8, 8' is adequately guided so long as the deflection of the drive drum 9 is less than the height h corresponding to the conicity of this drum.
In order to withstand the compression stresses resulting from the progressive crushing of the product between the belts 8 and 8', the conveyor belts 8 and 8' rub against steel sliding belts which are not illustrated in FIG. 2.
The major drawback of this embodiment is the considerable fouling of the two tension rollers 10, 11, 10', 11' whose surfaces are in contact with the faces of the belts 8, 8' which come into contact with the sized fibers forming the mat 12. In effect, these two tension rollers are therefore covered with sized fibers and become deformed, which causes increased stresses in the belts 8, 8', hence their misalignment. The belts are thus no longer guided and ultimately they tear. The width of the mineral wool mat hitherto was thus restricted to a maximum of 1.2 m.